The present invention relates to a dry-head or deluge-type alarm valve for permanently installed fire-extinguishing systems, especially sprinkler systems, with a blocking element that moves in a valve housing with an inlet and outlet and that, in the blocking position, operates in conjunction with the housing itself or with a seating ring rigidly mounted in it to tightly block the open cross-section of the housing.
Installing permanent fire-extinguishing systems, especially sprinkler systems, in large structures like department stores, industrial buildings, especially warehouses, parking garages, and similar spaces, to prevent damage from fire is known. Such systems can be wet- or dry-head. Since the piping leading to the sprinklers in wet-head systems are constantly full of water, such systems can only be employed in spaces where there is no risk of freezing. Dry-head systems, in which the section of piping leading from a source of extinguishing agent to what is called a dry-head alarm valve is full of water at a pressure of up to 10 bars, whereas the section leading from the dry-head alarm valve out into the spaces that are exposed to freezing is full of compressed air at a pressure of 3.5 bars for example, are accordingly used where there is a risk of freezing. When one or more of the sprinklers open, the air escapes and the water can set off the alarm while the valve opens and flows into the air-filled section of the piping and through the sprinklers to combat the fire.
Essentially two types of dry-head alarm valves are known, the differential type and the mechanical type. Whereas the differential type necessitates an air-blocked flap that is considerably wider than the open cross-section of the water channel, resulting in a large valve housing, the essential drawback of the mechanical type is that it is very complicated and difficult to maintain.